1. Field of the Invention
The present invention relates to a technology for ejecting ink onto a print medium to print images.
2. Description of the Related Art
In recent years, color printers of the type in which inks of multiple colors are ejected from an ink head have become popular as output devices for computers and are now widely used in processes in which images processed by computers are printed in numerous colors and gradations. Such printers are usually provided with improved print resolution and/or dot variation in order to improve image quality.
However, improving print resolution and/or dot variation is accompanied by an increase in the amount of data being processed. The resulting drawback is that, in particular, considerable time is needed to transfer data within a printing apparatus and between computers and the printing apparatus, resulting in reduced printing speed.
Accordingly, an object of the present invention is to provide a technique for increasing the number of available dot types to improve image quality while minimizing the reduction in printing speed.
In order to attain the above and the other objects of the present invention, there is provided a printing apparatus capable of selectively forming any of N types of dots which are different in at least one of an ink amount and a dot-formed position in a pixel area on a print medium. N is an integer of at least two. The printing apparatus comprises a print head and a drive signal generator. The print head has a plurality of nozzles and a plurality of ejection drive elements for ejecting ink drops from corresponding plurality of nozzles. The drive signal generator is configured to generate drive signals for driving the ejection drive elements to form one of the N types of dots in each pixel area in response to print signals. Each print signal for one pixel including 2 types of mask selection data. The 2 types of mask selection data are indicative of one type of masking signal among a plurality of types of masking signals corresponding to the N types of dots. The drive signal generator comprises an original drive signal generator, a mask signal generator, and a masking unit. The original drive signal generator is configured to generate an original drive signal having a plurality of pulses within a main scan period for a single pixel. The original drive signal is commonly applicable to the plurality of ejection drive elements. The mask signal generator is configured to select one type of masking signal from the plurality of type of masking signals in response to the 2 types of mask selection data in order to generate the masking signal. The masking unit is configured to selectively mask the plurality of pulses in the original drive signal using the generated masking signal in order to generate the drive signal to be supplied to the each ejection drive element.
In the printing of the present invention, the drive signals are generated using the mask signals selected with the two types of mask selection data. Therefore, it is possible to increase the number of dot types available by the printing apparatus, to thereby improve image quality.
The present invention can be realized in various forms such as a method and apparatus for printing, a method and apparatus for producing print data for a printing unit, and a computer program product implementing the above scheme.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.